Electromagnetic driving magnet



June 13, 1967 R, DgENER ETAL 23,.'31Z5J39;4

ELECTROMAGNETIC DRIVING MAGNET Filed NOV. lO, 1964 NM 53AM@ ,United States Patent O 3 325 139 ELECTROMAGNETIC DRIVING MAGNET Rudolf Diener, Ernst Wild, and Werner Roner, Zurich,

Switzerland, assignors to Eidima A.G., Zurich, Switzer- The invention relates to a solenoid type electromagnetic driving magnet having a rst movable magnetic core which can move axially relatively to a second stationary magnetic core having an energizing winding therearound. A disadvantage of known driving magnets of this kind is that the accuracy of their operation is unsatisfactory, the moving core not always taking up exactly the same position for a given energising current. The starting point for the invention is that the inaccuracies are due to the adhesive friction associated with the axial guiding of the moving core in the known driving magnets. It has been found that these inaccuracies can be obviated if, in accordance with the invention, the first (movable) core is guided by at least one ball bearing relatively to the second (stationary) core.

The invention also relates to a solenoid-operated valve utilising this driving magnet as a component thereof. In such use, the driving magnet has a stem which extends axially through the two magnet cores, the valve member being disposed on the bottom end of the stem; and extending around part of the length of the stem is a sleeve which is screwed into the second (stationary) magnetic core and against which two compression springs bear, the same being disposed around the stem and acting thereon in opposite senses; and the top end of the stem bears via an adjusting screw against a crosspiece of the moving (first) core, such crosspiece so engaging with the top end of the sleeve that rotation of the moving core rotates the sleeve and therefore alters the stressing of the two compressed springs in opposite senses.

The single gure forming the accompanying drawing is a view in longitudinal section of a solenoid operated valve, embodying the invention.

The solenoid valve shown comprises a casing 1 having an interiorly threaded inlet port 2 and an exteriorly threaded outlet port 3. A frusto-conical seating surface 6 of an otherwise cylindrical valve member seats on a valve seat 4 of the valve, the same being shown in the closed position. The valve member 5 is at the lower end of a stem 7, and the lower end of a metal spring bellows 9 is secured in a pressure-tight manner to the stem 7 above a collar 8 which follows the valve member 5. The top end of the bellows 9 is secured to a centrally apertured plate member 10 resting on a ring gasket 11 received in a recess in a sleeve 12. The sleeve 12 is engaged by a thread 13 in a tubular part 14 of the casing 1 and sealed by a gasket 15. The sleeve 12 has a stepped flange 16 whose t-op 'step 17 has engaging below it a separate ange 18 serving to retain, through the agency of screws 19, only one of which is visible, a cylindrical magnetic cup 20 on the sleeve 12 and therefore on the casing 1. The tubular part 14 is disposed above the entry port 2, the outlet port 3 extending laterally at right-angles to entry port 2.

The cup 20 is associated with an electromagnetic driving magnet designated generally as 21 and which is made of a ferromagnetic substance, such as iron, comprises an energizing winding 22, supply wires 23 which extend through an aperture 24 in the ange 18. The cup 2t) has a central tubular core 26 which extends upwards from 3', l Patented June 13, 1967 ICC- the cup base 25 and which terminates at the top in a pole piece 27 having a frusto-conical internal surface 28.

The core 26 has a continuous passage 29 receiving a sleeve 30 made of a low permeability substance, such as brass, and has an internal screwthread 31 at the bottom. An interiorly shouldered hollow cylindrical sleeve 32 has an external screwthread 33 at its lower end which is threadedly engaged in the thread 31. The upper end of a prestressed compression spring 34 bears against sleeve 32. The stem 7 extends coaxially through the sleeve 32, the lower end of the spring 34 bearing 'against a shoulder 35 of the stem 7. The force of the spring 34 yieldingly urges the valve member 5 downwardly against the seat 4 and against the entry pressure of the liquid, the prestressing of the spring 34 depending upon the position of the end 33 in the screwthread 31.

To turn the sleeve 32 and thus adjust the prestressing of the spring 34 without completely dismantling the soienoid valve, the top end of the sleeve 32 is -fo-rmed with two opposite rectangular recesses 36; extending therethrough is a crosspiece 37 which bridges a passage 38 in a moving magnetic core 39 and which is secured thereto. When the core 39 is rotated, the crosspiece 37 rotates the sleeve 32, so that the prestressing of the spring 34 can be adjusted in accordance with the pressure of the liquid flowing through the valve. The core 39 is covered by a cover 40 secured in a conventional readily releasable manner to the top end of the cup 20 and is therefore readily accessible even when the valve is in operation. The means providing the readily releasable connection between the cover 40 and the cup 20 are not shown. Provided that only the central part of the moving core 39' can be exposed, a Spanner or key or the like can be introduced into the passage 38 to engage those parts of the crosspiece 37 which are youtside the sleeve 32. The core 39 has a downwardly extending pole piece 41 having a frusto-conical outside surface 42 matching the frusto-conical inside surface 28 of the pole piece 27.

Disposed between the top part of the sleeve 32 and the moving core 39 in the passage 38 therein is a brass sleeve 43 which is formed with two rings of apertures 44 receiving balls 45. The sleeve 43 forms the cage of a ball bearing 46 whose raceways are formed `by the outside surface of the sleeve 32 and by the inside surface of the passage 38, the balls 45 rolling on these surfaces when the core 39 moves axially.

The top end of the stem 7 bears against the bottom end of an adjusting screw 47 screwed into the central part of the crosspiece 37. The screw 47 should be adjusted so that a small clearance is provided between the pole pieces 27 and 41 when the valve member .5 rests on the valve seat 4, to ensure that the pole pieces do not stick to one another in the closed position. A sleeve 50 bears against a clamping ring 49 engaging in an annular groove 48 at the top end of the stem 7. A helical compression spring 51 extends between the sleeve 50 and a shoulder 52 of the sleeve 32. The compression spring 51 yieldngly urges the stem 7 upwards-ie., to move the moving core 39 away from the stationary core 26 and therefore to move the valve member 5 oif its seat 4. When the sleeve 32 is rotated so that its screwthreaded end 33 is screwed upwards, the prestressing of the spring 35, which forces the valve member 5 downwards, -decreases and the prestressing of the spring 51 increases.

When the winding 22 is energized, the stationary core 26 pulls the moving core 39 downwards. The springs 35, 51 should be adjusted so that, with the winding 22 deenergized, the upwardly directed forces of the liquid pressure and of the spring 51 exceed the downwardly directed force of the spring 35 so that the valve is open. As the energizing current increases, the moving core 39 acts via the crosspiece 37 to move the stem 7 downwards gradually; since the force of the spring 51 increases during this downward movement, there is a diiferent equibrium position for each current value. Plotting the movement of the valve member in the closing direction against energizing current gives a substantially linear characteristie. Since the ball bearing 46 reduces very considerably the friction associated with the guiding of the core 39 i.e., of the stem 7-the characteristic is maintained much more accurately than in conventional solenoid valves. More particularly, valve operation is substantially unaffected by ageing and temperature effects, by the kind of lubrication, and by whether the equilibrium state is reached by a movement of the valve member 5 in the closing direction or in the opening direction. Nor are there jerky movements of the valve member 5, unlike what occurs in known valves where, particularly after the valve has been stationary for a prolonged time, there is a jerky changeover from adhesive friction to sliding friction, with a considerable impairment of accuracy of control.

Clearly, the electromagnetic `driving magnet 21-which includes the cup 20, the winding 22, the stem 7 and all the elements described under the references 25-52 inelusive-can be used in other ways-ie., it can be used whenever exact control of the movement of a member 5 by adjustment of an electric current is required.

The terms up, top, and down, bott-om as used hereinbefore and in the following claims are of course to be understood in the context that the driving magnet or valve is viewed in the position shown in the drawing.

We claim:

1. An electromagnetic driving magnet of the class described, comprising: a stationary magnetic core; a movable magnetic core coaxial with said stationary core and axially movable relatively thereto; an energizing winding around at least one of said cores for producing said axial movement therebetween; ball bearing means interposed between said cores for guiding said axial movement; a driving stem extending freely axially through said cores and said ball bearing means; a sleeve surrounding said stem throughout a portion of its length, said stem being threaded into the stationary core; two compression springs engaging said sleeve, said springs being disposed around the said stem and acting thereon in lopposite directions; a crosspiece carried by said movable magnetic core and engaging said sleeve whereby rotation of said movable core rotates said sleeve and therefore alters the stressing of the two compression springs in Vopposite senses; means connecting said movable core to said stem for displacement thereof in one direction, said springs yieldingly urging movement `o f said stem in the opposite directionl 2. Driving magnet as set forth in claim l, wherein said ball bearing means comprises a cage which can move axially relatively to the said sleeve and to said movable core, and balls retained in said cage which roll on the outside surface of the sleeve and on the inside surface of an axial passage of said movable core.

' 3. Driving magnet as set forth in claim 1, further comprising a ferromagnetic cup which houses said energizing winding, one end of said stationary core being connected to the base of said cup, the other end of said stationary core terminating in a pole piece which has a frusto-conical inside surface and into which a complementary frusto-conical outside surface lof a pole piece portion of said movable core extends.

4. Driving magnet as set forth in claim 1, further comprising a coverV for said movable core, `at least a portion of said cover being readily releasable for access to the central part -of said movable `core where the said crosspiece is located.

5. A solenoid-operated valve comprising an electromagnetic driving magnet according to claim 1; a valve member disposed at one end of said stem; an adjustment screw in said crosspiece, said adjustment screw bearing against the other end of said stem for causing said displacement thereof in said one direction; and a seat for said valve member, said adjustment screw varying the minimum gap between said cores when said winding is energized.

6. A solenoid-operated valve according to claim 5, further comprising resilient bellows separating said Valve member and said seat from said cores.

7. A valve according to claim 5, further comprising inlet and outlet ports communicating with said seat at opposite sides thereof, pressure fluid entering through said inlet port being directed to urge unseating of said valve member by movement thereof in said opposite direction. Y

8. A valve according to claim 7, further comprising a magnetic cup surrounding said energiing winding; a valve body in which said seat and said ports are located; and means connecting said cup to said Valve body.

References Cited UNITED STATES PATENTS 2/1919 Dinsmoor 335-262 5/1962 Lindsay 335-255 

1. AN ELECTROMAGNETIC DRIVING MAGNET OF THE CLASS DESCRIBED, COMPRISING: A STATIONARY MAGNETIC CORE; A MOVABLE MAGNETIC CORE COAXIAL WITH SAID STATIONARY CORE AND AXIALLY MOVABLE RELATIVELY THERETO; AN ENERGIZING WINDING AROUND AT LEAST ONE OF SAID CORES FOR PRODUCING SAID AXIAL MOVEMENT THEREBETWEEN; BALL BEARING MEANS INTERPOSED BETWEEN SAID CORES FOR GUIDING SAID AXIAL MOVEMENT; A DRIVING STEM EXTENDING FREELY AXIALLY THROUGH SAID CORES AND SAID BALL BEARING MEANS; A SLEEVE SURROUNDING SAID STEM THROUGHOUT A PORTION OF ITS LENGTH, SAID STEM BEING THREADED INTO THE STATIONARY CORE; TWO COMPRESSION SPRINGS ENGAGING SAID SLEEVE,SAID SPRINGS BEING DISPOSED AROUND THE SAID STEM AND ACTING THEREON IN OPPOSITE DIRECTIONS; A CROSSPIECE CARRIED BY SAID MOVABLE MAGNETIC CORE AND ENGAGING SAID SLEEVE WHEREBY ROTATION OF SAID MOVABLE CORE ROTATES SAID SLEEVE AND THEREFORE ALTERS THE STRESSING OF THE TWO COMPRESSION SPRINGS IN OPPOSITE SENSES; MEANS CONNECTING SAID MOVABLE CORE TO SAID STEM FOR DISPLACEMENT THEREOF IN ONE DIRECTION, SAID SPRINGS YIELDINGLY URGING MOVEMENT OF SAID STEM IN THE OPPOSITE DIRECTION.
 5. A SOLENOID-OPERATED VALVE COMPRISING AN ELECTROMAGNETIC DRIVING MAGNET ACCORDING TO CLAIM 1; A VALVE MEMBER DISPOSED AT ONE END OF SAID STEM; AND ADJUSTMENT SCREW IN SAID CROSSPIECE, SAID ADJUSTMENT SCREW BEARING AGAINST THE OTHER END OF SAID STEM FOR CAUSING SAID DISPLACEMENT THEREOF IN SAID ONE DIRECTION; AND A SEAT FOR SAID VALVE MEMBER, SAID ADJUSTMENT SCREW VARYING THE MINIMUM GAP BETWEEN SAID CORES WHEN SAID WINDING IS ENERGIZED. 